Microphysiology of synaptic transmission. Much of the current work revolves around a study of the distribution of chemoreceptors on the muscle surface, especially at synaptic and extrasynaptic regions. In addition, the participation of mitochondria in the release process of transmitters will be investigated. Studies on neurons in tissue culture. Investigations continue on sympathetic neurons in monolayer culture, using biochemical, physiological, electron-microscopical and histochemical techniques. In all cases, sympathetic neurons are dissociated from the superior cervical ganglion of newborn rats and grown under quasi-monolayer conditions. As reported earlier, the isolated neurons can either be grown in the presence of considerable numbers of non-neural cells (glia, fibroblasts, etc.) or in the virtual absence of these cells, by adding bicarbonate to a modified form of L-15 medium or by withholding bicarbonate, respectively. This has permitted studies of the influence of non-neural cells on the synthesis of transmitters and on synapse formation by the neurons. Studies of synaptic chemistry in the nervous system. The plan of studies during the coming year is to understand in chemical terms the differences between neurons that underlie their physiological function. Our studies will continue with the relatively simple lobster nervous system. Lobster neurons are large, and, compared to vertebrates, relatively few in number. It is possible to repeatedly dissect the same single physiologically identified axons and cell bodies from a series of animals allowing a detailed chemical analysis of these neurons. We will continue our efforts to find and identify cells using transmitter compounds other than GABA and glutamate, and concentrate on attempting to grow larval and adult lobster neurons in tissue and organ culture.